Coroutines should resolve with the generator return value

[felixfbecker]

PHP 7 has Generator::getReturn() to get the return value of a generator. That means code like this is possible:

coroutine(function () {
  $x = yield someAsync();
  if ($x->whatever) {
    return 'thisvalue';
  }
  $y = yield someOtherAsync();
  if ($y->whatever) {
    return 'thatvalue';
  }
  return yield $y->whatelse();

But currently coroutines will always use the last yield value, which makes control flow like above weird.

[evert]

This is a great idea, thanks!

[felixfbecker]

References that behave the same:
https://tc39.github.io/ecmascript-asyncawait/
https://www.npmjs.com/package/co
http://bluebirdjs.com/docs/api/promise.coroutine.html

This would simplify my code a lot, currently I have to yield another time before calling return to abort early.

[evert]

Do you think this is possible in a backwards compatible way? Or does this mean we need to do a 5.0.0 release?

[felixfbecker]

I think it's a breaking change because it changes the semantics. Any code that does

if ($whatever) {
  yield whatever();
  return;
}

will get null as resolve value (and it should be that way). Previously it would be the return value of whatever().

I think it's worth it though. Nobody is forced to update after all, but those who do and new projects benefit from a lot less boilerplate, cleaner semantics and shared behavior with how other implementations work. #43 is also kind of a breaking change in case you relied on the error being thrown.

[evert]

Well I fully agree that this should happen. So lets make this a priority and cut a v5.0. Sucks a bit to have a major version just after the last, but worth it!

[staabm]

agree, just do another major release. no worries.

[felixfbecker]

ETA for 5.0?

[evert]

Just released it!